A case study of intragenomic ITS variation in bryophytes: Assessment of gene flow and role of polyploidy in the origin of European taxa of the Tortula muralis (Musci: Pottiaceae) complex

Abstract

For the first time in bryophyte studies, we performed comprehensive cloning of the ITS region to reveal intraindividual variation of ITS sequences. We assessed relationships among morphologically defined taxa of the polyploid complex of the moss Tortula muralis. Our results detected a monophyletic T. muralis complex comprising T. muralis subsp. mura lis, T. muralis subsp. obtusifolia, T. lingulata, T. israelis, and T. edentula. The single accession of T. edentula was found nested within T. obtusifolia, and biphyletic T. israelis was found to be nested within T. muralis. With the exception of T. lingulata, intragenomic ITS sequence variation was high in the T. muralis complex. Most intraindividual sequences were nevertheless only weakly divergent, suggesting their origin via mutations exceeding the rates of concerted evolution. Markedly divergent sequences found within a single individual most probably resulted from gene flow among distant lineages of the complex. Such pattern of ITS variation challenges the traditional morphology-based taxonomy. No phylogenetic signal was associated with ploidy-level variation, suggesting a polytopic origin of the diploids. Interestingly, the pattern of ITS variation together with morphological evidence indicate the autopolyploid origin of some lineages, which renders the T. muralis complex the first group of mosses in which autopolyploidy is implied by molecular markers.

Patterns of hybridization in a multispecies hybrid zone in theRanunculus cantoniensiscomplex (Ranunculaceae)

“…First, it may result from hybridization between parents containing different ITS sequences (Baldwin et al ., ; Sang, Crawford & Stuessy, ). Second, divergent intra‐individual sequences might arise by molecular processes unrelated to hybridization, such as the accumulation of mutations, exceeding the rate of concerted evolution, nrDNA array multiplication or pseudogenization (Feliner & Rosselló, ; Kosnar et al ., ). In this study, the NJ tree distinguished four taxa, and intra‐individual combination of nrITS types of supposed parents was found only in the contact zone, suggesting that intra‐individual nrITS variation might result from hybridization rather than other molecular processes.…”

“…First, it may result from hybridization between parents containing different ITS sequences (Baldwin et al, 1995;Sang, Crawford & Stuessy, 1995). Second, divergent intra-individual sequences might arise by molecular processes unrelated to hybridization, such as the accumulation of mutations, exceeding the rate of concerted evolution, nrDNA array multiplication or pseudogenization (Feliner & Rosselló, 2007;Kosnar et al, 2012). In this study, the NJ tree distinguished four taxa, and intra-individual combination of nrITS types of supposed parents was found only in the contact zone, suggesting that intraindividual nrITS variation might result from hybridi- 87 1 0 0 1 0 1 1 0 3 1 0 8 1 0 9 1 1 0 1 1 1 1 1 5 1 1 6 1 1 7 1 1 8 1 1 9 1 2 0 1 2 1 1 2 4 _ 1 1 2 5 1 2 6 1 2 9 1 3 1 1 3 2 1 3 3 1 3 4 1 3 5 5 6 6 7 6 8 6 9 7 0 7 1 7 2 7 5 7 6 80 81 83 112 84 85 90 88 130 94 97 19 1 1 9 3 1 9 4 1 9 5 2 2 2 1 9 2 1 9 6 1 9 8 1 9 9 2 0 0 2 0 1 2 0 6 2 0 7 2 0 8 2 1 0 2 1 1 2 1 2 2 1 3 2 1 4 2 1 5 2 1 6 2 1 7 2 1 8 2 1 9 2 2 0 2 2 1 2 2 3 2 2 4 2 2 5 2 2 7 2 2 8 2 2 9 2 3 2 99 1 3 7 1 3 9 1 4 0 1 4 1 1 4 2 1 4 3 1 4 4 1 4 5 1 4 7 1 4 9 1 5 2 1 5 4 1 5 5 1 5 6 1 5 7 1 5 8 1 6 0 1 6 1 1 6 2 1 6 3 1 6 4 1 6 5 1 6 7 1 6 9 1 7 2 1 7 3 zation rather than other molecular processes.…”

Southern Scandinavian lowland populations ofRhytidium rugosum(Hedw.) Kindb. (Bryophyta, Rhytidiaceae) differ significantly from those in the mountains

“…Paralogous ITS haplotypes are rarely encountered in bryophytes (but see Košnar et al, 2012). However, the ITS chromatograms generated in this study did not show 'messy' patterns or noise that could suggest paralogy, and the 5.8S gene was invariable among all samples (cf.…”

Intraspecific genetic variation in selected mosses of Scandinavian interglacial refugia suggests contrasting distribution history patterns

“…Paralogous ITS haplotypes are rarely encountered in bryophytes (but see Košnar et al ., ). Thus, the ITS chromatograms generated in this study did not show ‘messy’ patterns or noise that could suggest paralogy, and the 5.8S gene was invariable among all samples (cf.…”